#neet
- From Ampere's circuital law for a long straight wire of circular cross-section carrying a steady current, the variation of magnetic field in the inside and outside region of the wire is : Answer: 4. a linearly increasing function of distance r upto the boundary of the wire and then decreasing one with 1/r dependence for the ou... 1
- Given below are two statements : One is labelled as Assertion (A) and the other is labelled as Reason (R).Assertion (A) : The stretching of a spring is determined by the shear modulus of the material of the spring.Reason (R) : A coil spring of copper… Answer: 4. (A) is true but (R) is false Assertion: when a spring is stretched, the wire of the coil is mainly twisted, which is a shear defo... 1
- The truth table for the given logic circuit is : Answer: 4. Truth table (A B C): 0 0 1; 0 1 0; 1 0 1; 1 1 0 Trace the circuit. The upper NAND gets A and B: Y₁=A· B . The lower NAND gets bar... 1
- A nucleus of mass number 189 splits into two nuclei having mass number 125 and 64. The ratio of radius of two daughter nuclei respectively is : Answer: 4. 5 : 4 Nuclear radius is R=R₀A^(1/3) . R₁/R₂=(125/64)^(1/3)=5/4 The ratio is 5:4 . Option (4). 1
- A wheatstone bridge is used to determine the value of unknown resistance X by adjusting the variable resistance Y as shown in the figure. For the most precise measurement of X, the resistances P and Q : Answer: 3. should be approximately equal and are small A Wheatstone bridge is most sensitive when all four arms have comparable resistance,... 1
- The area of a rectangular field (in m^2) of length 55.3 m and breadth 25 m after rounding off the value for correct significant digits is : Answer: 1. 14 × 10² Area =55.3×25=1382.5\ m² . In multiplication the answer keeps as many significant figures as the least precise number. 2... 1
- A big circular coil of 1000 turns and average radius 10 m is rotating about its horizontal diameter at 2 rad s^-1. If the vertical component of earth's magnetic field at that place is 2 × 10^-5 T and electrical resistance of the coil is 12.56 Ω, then… Answer: 4. 1 A Maximum emf in a rotating coil is ε_max=NBAω , with the field component perpendicular to the axis (vertical component here).... 1
- Two point charges -q and +q are placed at a distance of L, as shown in the figure.The magnitude of electric field intensity at a distance R (R>>L) varies as : Answer: 3. 1/R³ The two charges form an electric dipole with dipole moment p=qL . Their fields nearly cancel at a large distance. For Rgg L... 1
- A capacitor of capacitance C = 900 pF is charged fully by 100 V battery B as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance C = 900 pF as shown in figure (b). The electrostati… Answer: 4. 2.25 × 10⁻⁶ J Initial charge: Q=CV=900×10⁻¹²×100=9×10⁻⁸\ C . After connecting to an identical uncharged capacitor, charge is cons... 1
- Which statement regarding polymers is not correct ? Answer: 1. Thermosetting polymers are reusable. Key idea: thermosetting polymers are cross-linked and cannot be remoulded. Thermosetting pol... 1
- At 298 K, the standard electrode potentials of Cu^2+/Cu, Zn^2+/Zn, Fe^2+/Fe and Ag^+/Ag are 0.34 V, -0.76 V, -0.44 V and 0.80 V, respectively.On the basis of standard electrode potential, predict which of the following reaction can not occur ? Answer: 1. 2CuSO₄(aq) + 2Ag(s) → 2Cu(s) + Ag₂SO₄(aq) Key idea: a metal can displace another metal from its salt only if its standard reducti... 1
- The IUPAC name of an element with atomic number 119 is Answer: 2. ununennium Key idea: IUPAC temporary names use numerical roots: 0 = nil, 1 = un, 9 = enn, ending in -ium. Z = 119 means digits 1,... 1
- Given below are two statements :Statement I :In the coagulation of a negative sol, the flocculating power of the three given ions is in the order -Al^3+ > Ba^2+ > Na^+Statement II :In the coagulation of a positive sol, the flocculating power of the t… Answer: 4. Statement I is correct but Statement II is incorrect. Key idea: by the Hardy-Schulze rule, the coagulating ion is the one with ch... 1
- Which of the following statement is not correct about diborane ? Answer: 1. Both the Boron atoms are sp² hybridised. Key idea: in diborane each boron is sp³ hybridised, not sp² . Each B uses four sp³ orbit... 1
- RMgX + CO_2 dry ether Y H_3O^+ RCOOHWhat is Y in the above reaction ? Answer: 2. RCOO^(-M)g^+X Key idea: a Grignard reagent adds to CO₂ to give a magnesium carboxylate salt, which acid hydrolysis converts to th... 1
- What mass of 95% pure CaCO_3 will be required to neutralise 50 mL of 0.5 M HCl solution according to the following reaction ?CaCO_3(s) + 2HCl_(aq) → CaCl_2(aq) + CO_2(g) + 2H_2O_(l)[Calculate upto second place of decimal point] Answer: 3. 1.32 g Key idea: find moles of HCl, use the 1 : 2 stoichiometry, then correct for purity. Moles of HCl =0.5×0.050=0.025 mol. CaCO... 1
- Which amongst the following is incorrect statement ? Answer: 1. O₂^+ ion is diamagnetic. Key idea: write MO configurations and count unpaired electrons. O₂^+ has 15 electrons, with one electron... 1
- Amongst the following which one will have maximum 'lone pair - lone pair' electron repulsions ? Answer: 1. XeF₂ Key idea: compare the number of lone pairs on the central atom and their arrangement. XeF₂ : 3 lone pairs on Xe (trigonal bi... 1
- Choose the correct statement : Answer: 4. Diamond is sp³ hybridised and graphite is sp² hybridized. Key idea: diamond and graphite are both covalent forms of carbon with d... 1
- Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).Assertion (A) :In a particular point defect, an ionic solid is electrically neutral, even if few of its cations are missing from its unit cells.… Answer: 3. Both (A) and (R) are correct but (R) is not the correct explanation of (A) Key idea: missing cations with overall neutrality desc... 1
- The dimensions [MLT^-2A^-2] belong to the : Answer: 4. magnetic permeability Force has dimension MLT⁻² . Magnetic permeability appears in F=μ₀/4πI₁I₂ l/d , so μ₀ has dimensions of forc... 1
- Plane angle and solid angle have : Answer: 2. Units but no dimensions Plane angle is arc/radius (a ratio of lengths) and solid angle is area/radius squared, so both are dimens... 1
- When light propagates through a material medium of relative permittivity ε_r and relative permeability μ_r, the velocity of light, v is given by : (c - velocity of light in vacuum) Answer: 1. v = c/√(ε_r μ_r) In a medium, v=1/√(με) with μ=μ₀μ_r and ε=ε₀ε_r . Since c=dfrac1√(μ₀ε₀) , we get v=c/√(ε_rμ_r) . Option (1) is c... 1
- In the given nuclear reaction, the element X is :^22_11Na → X + e^+ + Answer: 4. ²²₁₀Ne The emission of a positron is beta-plus decay: a proton turns into a neutron, so the mass number stays the same and the at... 1